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We present near-infrared (NIR) broadband (0.80--2.42 $\mu$m) spectroscopy oftwo low mass X-ray binaries: V404 Cyg and Cen X-4. One important parameterrequired in the determination of the mass of the compact objects in thesesystems is the binary inclination. We can determine the inclination by modelingthe ellipsoidal modulations of the Roche-lobe filling donor star, but thecontamination of the donor star light from other components of the binary,particularly the accretion disk, must be taken into account. To this end, wedetermined the donor star contribution to the infrared flux by comparing thespectra of V404 Cyg and Cen X-4 to those of various field K-stars of knownspectral type. For V404 Cyg, we determined that the donor star has a spectraltype of K3 III. We determined the fractional donor contribution to the NIR fluxin the H- and K-bands as $0.98 \pm .05$ and $0.97 \pm .09$, respectively. Weremodeled the H-band light curve from \citet{sanwal1996} after correcting forthe donor star contribution to obtain a new value for the binary inclination.From this, we determined the mass of the black hole in V404 Cyg to be $M_{BH}=9.0^{+.2}_{-.6}M_{\odot}$. We performed the same spectral analysis for Cen X-4and found the spectral type of the donor star to be in the range K5 -- M1V. Thedonor star contribution in Cen X-4 is $0.94\pm.14$ in the H-band while in theK-band, the accretion disk can contribute up to 10% of the infrared flux. Weremodeled the H-band light curve from \citet{shahbaz1993}, again correcting forthe fractional contribution of the donor star to obtain the inclination. Fromthis, we determined the mass of the neutron star as $M_{NS}=1.5^{+.1}_{-.4}M_{\odot}$. However, the masses obtained for both systems shouldbe viewed with some caution since contemporaneous light curve and spectral dataare required to obtain definitive masses.

Near-Infrared Spectroscopy of Low Mass X-ray Binaries : Accretion Disk Contamination and Compact Object Mass Determination in V404 Cyg and Cen X-4